Here is an interesting article from Business Week on the possible side effects of a dye used in some MRIs and possible consequences for people with weak kidneys:
In May 2006 medical regulators in Denmark issued a warning that signaled trouble for General Electric (GE). Danish researchers noted that, over a four-year period, 25 patients in Denmark and Austria had suffered a rare and crippling disease after undergoing an MRI, the scanning procedure used to diagnose everything from brain tumors to blown knees. The patients had been injected with a GE dye that makes images more distinct. They all had weak kidneys before receiving the dye. The GE product, Omniscan, has since been linked to other cases of the disease, which appears to affect only MRI patients who have kidney problems. Similar drugs made by Bayer (BAY) and others have also been tied to the sometimes fatal ailment, nephrogenic systemic fibrosis (NSF).